Vehicular networks have emerged from the strong desire to communicate on the move [43,39,5,4,16]. Car manufacturers all over the world are developing industry standards and prototypes for vehicular networks (e.g., [12,6,37]). Existing works on vehicular networks often focus on low-bandwidth applications, such as credit card payment, traffic condition monitoring [13], Web browsing [5,4], and VoIP in ViFi [5]. They do not focus on supporting high-bandwidth applications (e.g., video streaming) in vehicular networks.
Cellular networks, despite good coverage, have only limited bandwidth and can incur high costs. For example, most cellular service providers in the US, like AT&T, T-mobile, Sprint, and Verizon, charge roughly $60/month for 5 GB data transfer and $0.2/MB afterwards. 5 GB data transfer can only support 0.1 Mbps for 111 hours (<5 days)! The cellular service price in many other countries are similar or even higher [40]. Moreover, many mobile broadband providers restrict or limit large data exchanges, including streaming audio, video, P2P file sharing, JPEG uploads, VoIP and automated feeds [46]. According to the international poll of 2700 Devicescape customers, 81% smartphone users prefer Wi-Fi over 3G cellular for data services [34]. This implies a stronger need for supporting high-bandwidth applications in vehicular networks using Wi-Fi. However, this is challenging since vehicles often move at high speed and thus the contact time between vehicles and access points (APs) tends to be short (e.g., [12] reported that 70% of connection opportunity is less than 10 seconds). In addition, it can be expensive to provide dense high-speed Internet coverage at a large scale. As a result, if vehicles fetch desired content on-demand from the Internet during their contact with an AP (as in [5,12]), the amount of data fetched may be insufficient to sustain the data rate required by applications such as video streaming when vehicles are outside the communication range of any APs.
A need, therefore, exists for a technique for enabling vehicular networks to support high-bandwidth applications, such as video streaming, that addresses these and other challenges.